This invention relates to apparatus and methods for exchange of a fluid between an apparatus reservoir and a reserve reservoir. The new apparatus is a pump that uses only one piston assembly in the central bore of an elongated tubular body to generate and control flow in a two circuit circulating fluid flow system to maintain fluid in an apparatus reservoir.
Historically circulating oil systems have been used over 100 years for maintaining oil levels in gearboxes and other fluid containing apparatus by supply from and overflow back to a reservoir. Such systems not only control the levels closely but also maintain cleaner oil due to the recirculation to the reservoir, which dilutes the contamination levels in the oil proportional to the oil quantity in the reserve. Other and newer systems for engine usage have two pumps: one to adjust a level by removal of excess oil in a crankcase in lieu of overflow, and one to return oil from a reservoir. These have gained acceptance largely in high priced applications. Problems with such systems are primarily cost, complexity and reliability. The use of two pumps for engine level control makes the system vulnerable to failure of one pump without failure of the other, leading to expensive complex construction to guarantee reliability.
U.S. Pat. No. 4,376,449 discloses a two pump circulating oil system utilizing two separate pumps having magnetically driven pistons that pump the two flow circuits of withdrawal and return, with the return of oil being under control of a trigger, this being the primary safety feature. There is a need for a pump that uses only one piston to generate both flow circuits, thus making sure that one flow circuit cannot operate without the other.
U.S. Pat. No. 4,496,287 discloses fluid displacement sensors with reciprocating tubular extensions. These sensors however are strictly limited in their design to the purpose of measuring the compressibility or displaceability of a fluid for information and do not anticipate the independent and primary utility of pumping two simultaneous flow circuits for level control. Also, U.S. Pat. No. 4,747,300 shows fluid displacement sensors and methods of enhancing sensing only.